There are numerous industry and other applications that require sorting of unordered items into a stream or an ordered arrangement based on a particular sorting order. Prior to sorting, the items to be sorted might be located not only in random order, but also on physically different structures, for example, on different conveyors. Typically, the items must not only be sorted locally on each conveyor, but must also be globally sorted over all the conveyors.
A computer system is sometimes used to automate the entire sorting process, or at least a portion of it, by deciding how to move the items. In order to electronically keep track of the items, some systems use bar codes or other computer-readable labels on the items. However, the items may be of different sizes, weight and materials, such that labels may not be appropriate. Labeling might also be prohibitive for other reasons, such as cost and time requirements. Additionally, labeling of items may hinder reuse of items in subsequent sorting procedures, as previous labels may have to be removed before application of new labels. Likewise, other devices for identifying locations of different items during a sorting process may not be convenient for certain applications.
A need therefore exists for a computerized system that will automate the sorting process while being able to combine items from several unsorted conveyors or streams into a single sorted output and keeping track of the items without additional labels or sensing devices. Furthermore, such a system should sort the items efficiently, optimally requiring only a single pass to sort all items.
Delivering, shipping, and storing mail items are a few, but by far not the only applications where such sorting systems are needed. Mail items must be sorted and resorted at several points in their progress. For example, at the destination post office, they need to be sorted into separate groups corresponding to an actual mail route. While there might be a mail sorting machine sorting individual pieces of mail into bins according to group assignments, some groups might be too large to fit into a single bin, and each of those “oversized” groups will be assigned to multiple bins. As a result, while the items are arranged in some order inside the bins, the bins themselves might be out of order. If the mail sorting machines leave the bins in different physical locations, then there is an additional task of sorting and combining the bins themselves such that they are returned to a desired location, serially and in order. The bins may be of different sizes, and labeling them is inconvenient because they are reused every time mail needs to be sorted. Also, bins might have a different groups assigned to them depending on the particulars of the mail sort, thus requiring relabeling prior to the sort. Therefore, an apparatus is needed that is capable of automatically sorting bins located on different conveyors without the bins themselves being externally labeled and returning these bins serially and in the desired order to an operator or a downstream processing system.